Add new field to mmfw_camcorder.ini for default encoded preview bitrate

Add new field to mmfw_camcorder.ini for default encoded preview bitrate

- Field name
 : "DefaultEncodedPreviewBitrate" in [VideoInput] category.
- Minor change
 : Change default encoded preview bitrate from 10M to 4M.
 : Remove duplicated set for bitrate and GOP interval.
 : Remove preview format restriction in commit function
   for MMCAM_ENCODED_PREVIEW_BITRATE attribute.

[Version] 0.10.247
[Issue Type] New feature

Change-Id: I8f87f9872685997d24dbe6009e8b865019d8c71f
Signed-off-by: Jeongmo Yang <jm80.yang@samsung.com>